For many years, catheters have been for a wide variety of medical procedures. Numerous types and variations of catheters have been developed for medical procedures. Among the advantages of using a catheter is that it is inserted into the patient through a small opening, either natural or made by a puncture. Typically, the catheter is used to perform a function deep within the body. The catheter enables the region of the body to be treated with minimal invasion and trauma. Often the use of a special purpose catheter to treat a condition may reduce the need for surgery. The use of a catheter often avoids long recuperative periods typical of more general surgical treatment.
By way of illustration, a catheterization procedure known as percutaneous transluminal angioplasty (PTA) is used to enlarge the lumen in an artery narrowed by plaque by delivering a catheter having a balloon at its end to the stenosisin (the narrowing) in the patient's artery. The balloon, once manipulated into the stenosis, can be inflated to unblock the artery and reestablish good blood flow through the artery. The procedure takes a few hours and the patient may resume activities, often at an increased level, within a day or two. By contrast, surgical intervention to remedy obstructed coronary arteries (coronary artery bypass surgery) is an extensive procedure, taking many hours, requiring surgical access through the chest wall to the patient's heart, typically requiring a recuperative period of many months.
Numerous other uses of a wide variety of catheters may include angiography, urinary, wound or chest drainage, optical examination and diagnosis of numerous lumens and body cavities and the like.
Catheters typically are made from materials suited particularly for the specific purpose to which the catheter is to be put. For example, the materials may be selected to provide a desired degree of flexibility or stiffness to the catheter or to provide regions of varying flexibility and stiffness along the length of the catheter. Materials may be selected to facilitate the ability of the catheter to transmit torque from the proximal end to the distal end of the catheter. In other instances the catheter may be made from materials having selected electrically conductive or insulative properties. Often it is desirable to provide either the inner or outer surface, or both surfaces, of the catheter with desired surface characteristics, such as lubricity or anti-clotting properties. It may be desirable to provide a catheter having optical capability by which light may be transmitted between the proximal and distal ends of the catheter. It ma be desirable to attach one or more balloons to the catheter and to provide inflation/deflation lumens for inflation and deflation of the balloons(s) as well as to provide other lumens for other purposes. Additionally it is a frequent requirement that the catheter maintain as small an outer diameter as possible, a requirement that often requires compromises to be made in the construction of the catheter such as, for example, dimensional compromises in wall thickness, lumen size or the like.
Catheters frequently have multiple requirements or functions. For example, often it is desirable that part of the catheter be stiff while another part of the catheter be flexible. It is common for catheters to have portions that are electrically conductive alternated with portions that are insulative. Thus, catheters often have different constructions either in the materials, components or shape or the like at different locations along the catheter.
A typical catheter construction involves the extrusion of a selected polymeric material into a tubular catheter shaft having one or more lumens. A wide variety of polymeric materials are in common use such as polyvinyl chloride, polyethylene, polytetrafluoroethylene, urethane formulations, polyesters and the like. In a typical catheter construction other elements are added to the shaft such as balloons, fittings, connectors, coatings, transducers, optical fibers, conductors, electrodes, braids and the like. Numerous finishing operations typically are required in order to assemble the catheter. The manufacturing procedure is labor intensive. Other techniques for manufacturing a catheter shaft also include the molding as well as the repetitive coating of multiple layers built up on a mandrel. Often the manufacturing procedure imposes limitations on the nature and the number of characteristics that a particular catheter might incorporate.
As catheterization procedures have developed, there has been an increasing tendency to build catheters with thinner walls. By making the catheter with a thinner wall, the catheter is provided with increased internal space for additional lumens or the ability to increase the size of the existing lumen(s) without increasing the overall outer diameter of the catheter. It also may enable the outer diameter of the catheter to be reduced so that the catheter may be more easily advanced into the body lumen or internal body location to be treated. As the demands for higher performance, multiple function catheters has increased, it has become increasingly difficult to manufacture such thin wall, multi-function catheters utilizing existing catheter manufacturing techniques. Among the difficulties is that catheters having very thin walls may tend to kink when curved or bent, thus tending to close off the catheter lumens.
It is among the general objects of the invention to provide a new method for making catheters and a resulting new catheter construction which avoids many of the difficulties presented in prior catheter manufacturing techniques.